`diff'
------

diff(RAT[,VARN]*)
diff(RAT,VARLIST)
     :: RAT $@$r(J VARN $@$"$k$$$O(J VARLIST $@$NCf$NJQ?t$G=g<!HyJ,$9$k(J.

RETURN
     $@<0(J
RAT
     $@M-M}<0(J ($@=iEyH!?t$r4^$s$G$b$h$$(J)
VARN
     $@ITDj85(J
VARLIST
     $@ITDj85$N%j%9%H(J

   * $@M?$($i$l$?=iEyH!?t$r(J VARN $@$"$k$$$O(J VARLIST $@$NCf$NJQ?t$G=g<!HyJ,$9(J
     $@$k(J.
   * $@:8B&$NITDj85$h$j(J, $@=g$KHyJ,$7$F$$$/(J. $@$D$^$j(J, diff(RAT,x,y) $@$O(J,
     diff(diff(RAT,x),y) $@$HF1$8$G$"$k(J.

     [0] diff((x+2*y)^2,x);  
     2*x+4*y
     [1] diff((x+2*y)^2,x,y);
     4
     [2] diff(x/sin(log(x)+1),x);
     (sin(log(x)+1)-cos(log(x)+1))/(sin(log(x)+1)^2)
     [3] diff(sin(x),[x,x,x,x]);
     sin(x)

